ES2941466T3 - Infill for artificial grass system and manufacturing process - Google Patents

Abstract

An artificial grass system includes a turf assembly having a grass support and stands of artificial grass blades that extend from the grass support to form a layer of artificial grass. The infill material is placed between the artificial grass blades and on top of the grass backing. The fill material has a composition of sand in an amount within the range of about 80 to about 98 percent of the fill by dry bulk weight, and organic particles in an amount within the range of about 2 to about 20 percent of filling. by dry bulk weight. (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Infill for artificial grass system and manufacturing process

Background of the invention

The present invention relates generally to artificial turf systems of the type used on sports fields, ornamental lawns and gardens, and playgrounds. In particular, the present invention relates to artificial turf systems having infill material as part of the upper structure of the turf assembly.

Artificial turf systems are commonly used on sports playing fields, and more particularly on artificial playing fields. Artificial grass systems can also be used on synthetic turfs and golf courses, rugby pitches, playgrounds and other types of fields or similar floor coverings. Artificial turf systems typically comprise a turf assembly and a foundation, which can be made from materials such as asphalt, rolled earth, compacted gravel, or crushed rock. Optionally, a resilient underlayment pad or underlayment layer can be provided between the turf assembly and the foundation. The turf kit is typically made of plastic strands, artificial grass blades attached to a turf backing. An infill material, which is typically a mixture of sand and ground rubber particles, can be applied between the vertically oriented artificial grass blades, typically covering the bottom half or 2/3 of the blades.

In 1965, artificial turf was introduced to the United States as a green carpet made of nylon fibers. A polyurethane padding was laminated to the underside of the mat to reduce the risk of injury resulting from impact with the surface. For most of the next decade, few changes were made to the original turf design, despite the increasing number of complaints from teams and players about various injuries occurring on the fields. Synthetic grass carpet was introduced to Europe in 1970. Instead of nylon fibers, it was made of polypropylene. Less expensive than nylon, polypropylene was softer and more pleasant on players' skin.

In the late 1970s, a second-generation synthetic turf system was introduced, with longer, more widely spaced knots. Sand was spread between the fibers to keep the synthetic turf blades upright and create enough firmness and stability for the players. The playing characteristics and safety on these pitches were not comparable to natural grass and surface abrasion was still a problem.

Following the advent of sand irrigated artificial turf pitches, technological advances gave rise to a new type of synthetic turf pitch, which is currently in use. This grass has even longer fibers that are even further spaced apart in the mat compared to second generation "sand filled" and "sand lined" systems. These fibers are usually made of polyethylene, which is more skin-friendly than polypropylene. These fields are spread or "filled" with various mixtures of silica sand and/or recycled tires (crumb rubber commonly known as SBR-styrene-butadiene rubber). This third generation system attempts to incorporate shock attenuation properties into the filler material. Variations on third generation systems include filler materials such as thermoplastic elastomer granules, rubber coated sand, acrylic coated sand, EPDM granules, and organic materials such as ground coconut shell and cork.

There are multiple negative aspects associated with the use of rubber granules as an infill material for artificial turf, or as an infill component in combination with sand. Rubber granules are created by shredding or fracturing post-consumer car and truck tires. The black color and synthetic composition of the rubber granules absorb radiant solar energy, causing the playing surface to overheat. The heat problem is exacerbated by the polyolefin fibers in synthetic grass. Surface temperatures exceeding 170°F are frequently measured in this type of field. Most sports facilities with this type of athletic fields incorporate a cooling (irrigation) system. These "cooling" systems are only marginally effective in hot weather conditions. The unpleasant chemical odor that comes from the field surface in hot weather conditions is also a frequent complaint. Ground rubber from tires also contains several known carcinogens, the health effects of which are not yet fully understood. By comparison, natural sports turf stays relatively cool compared to ambient temperatures. Although natural grass requires a higher degree of maintenance compared to artificial grass, the abundance of sports fields in hot climatic regions is natural.

Disposal of synthetic filler materials, including black rubber granules, is becoming more expensive and problematic. A typical full-size sports field can contain between 100 and 180 tons of rubber granule infill, which may or may not be mixed with sand. This material is rarely reinstalled after the life of the synthetic turf, which is typically 8-10 years. Due to prolonged exposure to UV rays and abrasion, the elasticity of rubber granules deteriorates, which means that the material is not suitable for reuse and can only be disposed of in a landfill. Not all landfill facilities will accept rubber granules due to their chemical composition, which may result in longer transport distances being required for disposal.

There are concerns that some of the chemical content of rubber fill may have undesirable effects on the environment and that runoff from rubber fill systems may adversely affect marine life. Elevated levels of zinc are often observed in rainwater from artificial turf fields with black rubber granules. Other noteworthy issues are that rubber filler is considered dirty and less than ideal as a surface material. On these athletic fields, rubber particles stick to players' clothing due to static electricity and often find their way into shoes, ear canals, and eyes. Rubber particles often spatter the turf system after impacts or cleat cutting and dragging. Aesthetically, artificial turf fields with ground rubber waste appear less green compared to natural grass.

There are alternatives to filler from black ground rubber waste, albeit at higher costs. Imported "organic" fillers are composed either exclusively or primarily of ground coconut shell. A backfill material includes a mixture of coconut shell, rice husk to facilitate drainage, and cork particles to prevent excessive compaction. These organic fill materials are very light and are installed as a top layer over a sub-layer of sand, with the sand used for ballast and stability. These infill materials are effective in reducing gaming surface temperatures and provide a more natural interface between players and the surface. However, the practice of installing a sand layer of subfloor with a primarily coconut shell topcoat has several disadvantages, including a higher purchase price, increased maintenance requirements, excessive wear and tear, and rapid evaporation. The organic fill materials used today come primarily from Indonesia and Europe, making the purchase price plus shipping a surcharge for field facilities.

As a direct interface between players and the surface, organic material breaks down under impact into smaller particles, resulting in a more compact layer and reduced depth. This problem is especially serious if the field is used in dry conditions, which makes the organic material brittle. To mitigate this problem and prevent excessive wear on the synthetic turf fibers, organic infill requires frequent replacement of the material known as a "top liner." This increases costs and maintenance efforts.

The organic filler helps keep surface temperatures lower through evaporation. To perform this function, the field must be irrigated frequently. Moisture is absorbed into the organic material and excess water is drained from the surface system through the sand sublayer. The thickness of the organic layer is typically 15 to 20 mm deep. On a synthetic turf field this top organic layer is exposed to direct sunlight. Synthetic turf fibers and organic material heat up from this exposure. Moisture in the system evaporates, thus releasing heat, and this evaporative cooling helps maintain a cooler surface. However, in hot weather conditions, this effect may only last a few hours. Irrigation is then required to rehydrate the system.

Pure cork granules have also been used as fill material in combination with silica sand, either in a mixed or layered arrangement. Cork provides a degree of cooling benefit relative to ground rubber in tires, but the flotation, lateral migration, and vertical migration of this infill system have proven problematic during and after heavy rain. Excessive static electricity and excessive spatter from the filler are other problems associated with cork filler.

Examples of other alternative filler materials include rounded silica sand, virgin EPDM rubber granules, thermoplastic elastomer (TPE) granules, polyethylene granules, coated acrylic sand, and polyurethane coated SBR granules. Although some of these materials reduce or mitigate the harmful chemicals contained in ground rubber from tires, they are expensive and do not significantly address the problem of surface heat. The performance of these materials in terms of shock attenuation is also somewhat inferior to that of rubber granules made from ground rubber from tires. Other than sand, these other synthetic fill materials have been used to some extent.

Recent studies have shown that head and lower extremity injuries are even more common and severe on traditional third-generation synthetic turf fields compared to natural sports turf. Traditional synthetic turf fields deteriorate over time due to UV exposure, excessive surface temperatures that prematurely age synthetic fibers, and excessive infill compaction. Performance and safety values vary greatly between a new synthetic turf field and a field that is 5 years old or older.

Pristine natural sports turf is still considered the healthiest and preferred playing surface. Relatively cool surface temperatures, ideal grip and traction, effective shock absorption for safety, and natural aesthetics are all attributes that make natural grass desirable over synthetic turf. High-end, sand-based natural turf root zones consist primarily of sand for firmness and drainage, with a small percentage of peat and/or silt to stabilize the sand, stimulate growth and retain moisture. However, natural sports turf is difficult and expensive to maintain in pristine condition, especially when heavily used. Watering, mowing, seeding, aerating, and fertilizing are all necessary to maintain natural grass. These aspects of natural grass maintenance are aggravated in certain indoor applications or the indoor environment precludes the application of natural grass completely.

To date, all artificial turf infill materials, as part of a surface system, present some degree of compromise and disadvantage, whether due to temperature, chemical concerns, safety, performance, waste disposal, maintenance, or cost. . The padding material has typically been formulated to provide a resilient or cushioning effect to absorb at least a portion of the players' impact loads. However, some of the materials used create environmental and health effects that are less than desirable. Furthermore, due to wear and degradation properties, the support and cushioning properties of these filler layers can change negatively over time. Therefore, it would be desirable to provide an improved infill material that more closely mimics natural turf's impact and performance characteristics.

Document US20130302614A1 discloses plant biomass particles coated with a biological agent such as a bacterium or a seed, characterized by a dimension of length (L) aligned substantially parallel to a grain direction and defining a substantially uniform distance along the grain. the grain, a width dimension (W) normal to L and aligned to the cross grain, and a height dimension (H) normal to W and L. In particular, the L x H dimensions define a pair of substantially parallel side surfaces characterized by substantially intact longitudinally disposed fibers, the dimensions W x H define a pair of substantially parallel end surfaces characterized by transversely cut fibers and cracking at the ends between the fibers, and the dimensions L x W define a pair of substantially parallel top and bottom surfaces parallel.

Document WO2016205087 A1 discloses an artificial turf system with grass-like polymeric turf fibers and infill particles sandwiched between said turf fibers. At least part of the filler comprises composite synthetic particles containing a thermoplastic polymer and cellulose fibers, wherein the thermoplastic polymer is a matrix that binds the other components of each synthetic particle into a composite particle.

Compendium of the invention

The present invention relates to an artificial turf assembly including artificial grass blades surrounded and supported by an infill material. Backfill material includes sand and additional materials.

An infill material for an artificial turf system having a plurality of wood particles is disclosed. Each particle defines a length dimension greater than a width or thickness dimension, and each particle length dimension is oriented generally parallel to a grain structure of each particle. The length dimension is in a range of about 1 mm to about 10 mm. The length and one of the width or thickness dimensions define an aspect ratio within a range of 4:1 to 10:1. Each particle maintains a water-absorbing property that allows the particle to retain water and release it over time to disperse the heat of the filler material, in which the wood particles are processed by tumbling or abrasion to round the edges of wood particles such that the edges of the wood particles are smoothed compared to a cut surface having a sharp, angular edge shape.

An artificial turf assembly includes a turf mat having a plurality of separate synthetic grass blades and infill material dispersed on the turf mat between the turf blades. The fill material includes sand and a plurality of wood particles, each particle defining a length dimension greater than a width or thickness dimension. Each particle length dimension is oriented generally parallel to a grain structure of each particle. The length dimension is in a range from about 1 mm to about 10 mm, and the length and one of the width or thickness dimensions define an aspect ratio within a range from 4:1 to 10:1. Each particle maintains a water-absorbing property that allows the particle to retain water and release it over time to disperse heat from the fill material.

An artificial turf system includes a turf mat having a plurality of separate synthetic turf blades attached to a backing layer, an underlayment layer, and an infill material dispersed over the turf mat. The underlayment layer is formed, at least in part, from expanded polyethylene or polypropylene bead material having a density in the range of 45-70 g/l. The fill material includes sand and a plurality of wood particles, each particle defining a length dimension greater than a width or thickness dimension. Each particle length dimension is oriented generally parallel to a grain structure of each particle. The length dimension in a range from about 1 mm to about 10 mm, and the length and one of the width or thickness dimensions define an aspect ratio within a range from 4:1 to 10:1. Each particle maintains a water-absorbing property that allows the particle to retain water and release it over time to disperse heat from the fill material. The turf mat and infill material disposed on the turf mat define a first spring constant and the underlayment layer defines a second spring constant that is more conformal than the first spring constant. In another embodiment, the second spring constant of the subfloor layer is associated with a deflection control layer and the subfloor layer further defines a third spring constant associated with a center section such that the first spring constant is stiffer than the third spring constant and the third constant of the spring is stiffer than the second spring constant. In yet another embodiment, the underlayment layer includes a plurality of projections disposed across a top bearing surface of the underlayment in contact with the turf mat.

Various aspects of the present invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying figures.

Brief description of the figures

Figure 1 is a schematic elevational cross-sectional view of an artificial turf system.

Figure 2 is a cross-sectional elevation view of a prior art turf system illustrating a deflection response of infill material to an applied load.

Figure 3 is a cross-sectional elevation view of one embodiment of a turf system in accordance with the invention illustrating a deflection response of the system to an applied load.

Figure 4 is a data table showing impact test results for one embodiment of a turf system in accordance with the invention when tested in dry conditions.

Figure 5 is a data table showing impact test results for one embodiment of the turf system according to the invention when tested in wet conditions.

Figure 6 is a data table showing impact test results for another embodiment of a turf system in accordance with the invention having an alternative underlayment configuration.

Figure 7 is a data table showing the parameters and certain endurance test results of one embodiment of a turf system.

 Figures 8-11 are photographs showing the shape and size ranges of the wood particle components of the fill material before and after testing.

Figure 12 is a schematic illustration of a log as the source of the wood filler particles showing the relative orientation of the chips prior to formation.

Figure 13 is a schematic illustration of a chip formed from the log of Figure 12.

Fig. 14 is a sketch showing the basic operating features of a wood chipper with a disk-shaped chipper blade.

Fig. 15 is a sketch showing the basic operating features of a wood chipper with a drum-shaped chipper blade.

Figure 16 is a data table showing the evaporative cooling effect of one embodiment of wood particle filler.

Comparison of evaporative cooling of uninfilled turf, rubber infill, and wood particle infill Figure 16

Figure 17 is a graph comparing the stress/strain response curve profiles of underlayment materials and rubber infill to natural turf.

Detailed description of the preferred embodiment

The turf system shown in Figure 1 is indicated generally at 10. The turf system includes an artificial turf assembly 12, an underlayment layer 14, and a foundation layer 16. The foundation layer 16 may comprise a layer of crushed stone or aggregate 18, or any other suitable material. Numerous types of foundation layers are known to those skilled in the art. The crushed stone layer 18 can be placed on a subbase, such as compacted earth, a poured concrete base, or an asphalt paving layer (not shown). Alternatively, the subfloor layer 14 can be applied over the asphalt or concrete base, omitting the crushed stone layer, if desired. In many turf systems used on an athletic field, the foundation layers are leveled in a contour with the goal of allowing water to drain to the perimeter of the field and not pooling water anywhere on the surface.

The artificial turf set 12 includes a turf mat 12A having strands of synthetic grass blades 20 attached to a turf backing 22. A filler material 24 is applied to the blades 20 of grass. The filler material according to the invention includes sand particles 24a, which may be of a generally wide variety and type, and wood particles 24b, which may be provided in a layered arrangement along the length of the sheets 20. of grass or as a mixture. Other constituent materials may also be included, as will be explained in detail below. The synthetic grass blades 20 can be made from any material suitable for artificial turf, many examples of which are well known in the art. Synthetic grass blades are typically approximately 50mm in length, although any length can be used. The artificial grass blades 20 are placed, woven or knotted securely onto the backrest 22. One way of sheets that can be used is a relatively wide polymer film that is cut or fibrillated into several sheets of thinner film after the wide film is inserted into knots in the backing 22. In another form, the sheets 20 are relatively thin polymer (monofilament) that resemble individual blades of grass without fibrillating. Both can be colored to look like blades of grass and are attached to the backrest 22.

The backing layer 22 of the turf assembly 12 is typically itself water porous, but is often optionally coated with a water impervious coating 26A, such as polyurethane, to anchor the turf fibers in the backing. To allow water to drain vertically through the back 22, the back can be provided with separate holes 25A. In an alternative arrangement, the water impervious coating is applied partially or completely and then scratched off in some parts, such as the drainage portion 25B, to allow water to drain through the backing layer 22. The grass fiber sheets 20 are inserted into knots typically on the backing 22 in rows that are evenly spaced, such as rows that are spaced between about 4 millimeters and about 19 millimeters apart, for example. The incorporation of the grass fibers 20 into the backing ply 22 sometimes results in a series of spaced-apart, substantially parallel, urethane-coated ripples or ridges 26B on the bottom surface 28 of the backing ply 22 formed by the knots of grass. the blades of grass. The ridges 26B may be present even when the fibers are not exposed.

The infill material 24 of the turf assembly 12 is placed between the artificial grass blades 20 and on top of the backing 22. The infill material 24 is applied in an amount that covers the underside of the synthetic grass blades 20 so that the tops of the sheets protrude above the padding material 24. Typically, the padding material 24 is applied to add stability to the field, improve traction between the athlete's shoe and the playing surface, and improve shock attenuation on the field.

The turf underlayment layer 14 comprises expanded polyolefin foam beads, which may be expanded polypropylene (EPP) or expanded polyethylene (EPE), or any other suitable material. Foam beads are closed cell (impervious to water) beads. In one manufacturing process, the beads are originally made as small solid plastic pellets, which are then processed in a controlled pressure chamber to expand into larger foam beads having a diameter within the range of about 2 to about 5 millimeters. millimeters. The foam beads are then blown into a closed mold under pressure to make them tight. Finally, steam is used to heat the surface of the mold so that the beads soften and melt together at the interfaces, forming the turf underlayment layer 14 as a solid material that is impervious to water. Other manufacturing methods may be used, such as mixing the beads with an adhesive material or glue to form a slurry. The slurry is then molded into shape and the adhesive is cured. Suspension mix underlayment can be porous through the thickness of the material to drain water. This porous subfloor structure can also include another drainage feature discussed below. The final EPP material can be manufactured in different densities starting with a bead of different density or by any other procedure. In one embodiment, the density range of the underlayment layer 14 is in a range of about 45 grams/liter to about 70 grams/liter. In another embodiment, the range is from 50 grams/liter to 60 grams/liter. The material can also be made in various colors. The resulting subfloor structure, made by the vapor molding or slurry mix process, can be formed as a water-impervious subfloor or a porous subfloor. These resulting subfloor layer structures can further include any of the drainage, deflection, and interlocking features discussed below.

The ability to tailor the load reactions of the subfloor, turf, and infill material as a complete artificial turf system requires consideration and adjustment of competing design parameters, such as a body impact characteristic, a response characteristic athleticism and a characteristic of the response of the ball. The body impact characteristic relates to the ability of the turf system to absorb energy created by player impacts with the ground, such as but not limited to tackles common in American football and rugby union. Body impact characteristic is measured using standardized test procedures such as ASTM-F355 in the United States and EN-1177 in Europe. Turf systems that are designed for a softer or more shock absorbing response tend to protect better against head injuries, but offer reduced or unoptimized performance for the athlete and the ball. This is particularly true of systems that use resilient fill.

The athletic response characteristic relates to athletes' performance responses during running and can be measured using a simulated athlete profile, such as the Advanced Artificial Athlete. Athlete performance responses include factors such as the turf's response to running loads such as heel and forefoot contact and the resulting load transfer. The turf's response to these running load characteristics can affect performance and player fatigue. Ball response to a particular turf system may include variations in ball bounce height depending on the firmness of the surface; ball roll, which is affected by the friction of the ball against the turf fibers and infill material; and ball spin, which is affected by how the ball slides or grips against compacted or loose infill material as it bounces off the turf.

The underlayment layer and turf assembly each have an associated energy absorption characteristic, and are balanced to provide adequate system response for turf system use and for meet the required body impact characteristics and athletic response characteristics.

To meet the particular needs of players, as well as to meet the rules and requirements of a particular sport, it may be necessary to modify various design parameters of the artificial turf system. The particular sport, or the range of sports and activities performed on a particular artificial turf system, will dictate the required overall energy absorption level of the system. The energy absorption characteristic of the underlayment layer can be influenced by changes in material density, protrusion size and geometry, panel thickness, and surface configuration. These parameters can be further categorized under a broader panel material factor and underlayment panel geometry factor. The energy absorption characteristic of the turf assembly involves properties of the infill material, such as compaction of the material, water absorption and retention, particle decomposition, and depth. The infill material may comprise a mixture or separate layers of sand and synthetic or organic particles in a suitable ratio to provide adequate exposure of the synthetic grass blades, water drainage, stability and, in some cases, energy absorption.

As schematically shown in figure 3, these characteristics can be understood as springs in series. As shown in Figure 3, the subfloor layer 14 defines a spring constant k1 through a central section, identified as zone CC, and a spring constant k2 associated with a deformation control layer, which may include a deformation structure such as projections, of the BB zone. Alternatively, zone BB can be a layer of material without projections but which has the flexibility index k2. Said layer associated with the zone BB can be integrally formed with the core section CC or applied on the core section CC. The turf assembly 12 defines a spring constant k3 which acts through zone AA in response to applied loads, such as shock loads or running loads as illustrated. Each spring pattern represents a part of the response characteristic of the layer and may be further characterized by one or more springs, in series or parallel, within each layer. A damping component can also be included in the characterizations of the layers. The infill 24 provides a substantially stiffer apparent spring constant k3 value for the spring representing the turf assembly 12 than would be associated with more resilient infill compositions, such as those that include rubber-based materials. The padding 24 is stiffer when loaded in compression in an impact, such as the impact event on a player being tackled, to allow for load transfer to the foundation layer 14 where the properties of the structure and materials subfloor dominate the reactive force returned to the player. In one embodiment, the relative spring constants and stiffness of the corresponding sections, indicated from stiffest to most compliant, are preferably ordered as k3 > k1 > k2, where the section of the subfloor having the carpet contact surface of turf is more conformable than either the turf assembly or the subfloor core, as shown in Figure 3. From a macroscopic perspective, the infill 24 provides a load transfer to the subfloor layer similar to compacted sand. However, the wood particles 24b do not compact like sand when analyzed at a particle-to-particle level of interaction. Instead, the particles 24b maintain limited movement relative to one another due to the size, dispersion and interactions of the particles, and the grain orientation of the wood particles 24b. The firmness of the particles and the limited movement of individual particles provide a natural grass feel, even with surface irregularities that are the result of athletic activity. Rubber-based resilient padding, on the other hand, tends to highlight these surface irregularities that cause a lack of security in an athlete's foot.

As a consequence of the size, aspect ratio, and orientation of the vein, the motion of the particles differs from that of a granular particle, such as sand. The sand particles will compact and form a structure much like stones stacked to form a wall. Wood particles 24b will be oriented in a more random configuration where through-thickness stiffness properties provide load transfer to the subfloor, but shear properties allow for some twisting movement, such as cleats engaging the surface. of padding, without loss of traction, just like an athlete who suddenly changes direction. The wood particles 24b are sized such that the particle interactions provide sufficient supportive grip to withstand the tensile stress, but sufficient relative movement to prevent the dowels from sticking in place, causing sprains and related injuries. with the ankle, leg and hip. The orientation of the grain with respect to the longitudinal dimension of the particle 24b allows deflection of the localized particles without fragmentation into small pieces or fragments of granular size and shape.

The turf set 12 also provides the feel of the field when running, as well as the bounce and roll of the ball in sports such as soccer (American football), field hockey, rugby and golf. The turf assembly 12 and the turf underlayment layer 14 work together to achieve the right balance of firmness when running, softness (shock absorption or energy absorption) on landings, bounce and ball roll, etc. To counteract the changing characteristics of the course over time, which affect the bounce and roll of the ball and the feel of the course for the running athlete, in some cases the infill material can be maintained or supplemented by adding more padding and using a raking machine or other mechanism to fluff up the padding to maintain proper feel and shock absorption.

The hardness of the athletic field affects performance on the field, as hard fields allow athletes to run faster and turn faster. This can be measured, for example, in the United States using the ASTM F3189-17 test standard, and in the rest of the world with the FIFA, IRB (International Rugby Board) test standards. FIH (International Hockey Federation) and ITF (International Tennis Federation). In the United States, another feature of the resilient turf underlayment layer 14 is to provide increased impact attenuation of the infilled turf system by up to 20 percent during heel and forefoot running loads. A greater amount of attenuation can cause athletes to become overtired and not perform their best. An athlete's perception threshold to variation in turf stiffness compared to natural turf stiffness (with running loads based on US testing) is believed by some to be a difference in stiffness deviations of plus or minus minus 20 percent. The FIFA test requirement has minimum and maximum values for shock attenuation and deformation under running loads for the entire turf/subfloor system. Artificial turf systems with shock attenuation and deformation values between the minimum and maximum values simulate the feel of natural grass.

Impact energy absorption is measured in the United States using ASTM F355-A and F355-E standards, which give ratings expressed as Gmax (maximum acceleration on impact) and HIC (head injury criteria). The head injury criterion (HIC) is used internationally. There may be specific imposed requirements for maximum acceleration and HIC for athletic fields, playgrounds, and similar facilities.

The turf assembly 12 using the wood particles 24b as a constituent element is advantageous in that in one embodiment it is somewhat slow to regain shape when deformed by compression. This is favorable because when an athlete runs on a field and deforms it locally under the shoe, it is undesirable for the playing surface to recover so quickly that the shoe looks "pushed or pushed back" when lifted off the field. surface. This recovery effect provides an unnatural energy restoration in the shoe. By making the turf set 12 have adequate recovery, the field will be perceived more like natural grass that does not have much resiliency. The turf assembly 12 can be designed to provide the proper material properties that will result in favorable limits on recovery values. The turf set 12 can be designed to complement specific turf designs for optimum product properties. As shown in Figure 17, the response curves of various components of the artificial turf set are compared to the response of a natural grass pitch. While the magnitudes of the response curve values are not represented and therefore not directly comparable, the profiles of these curves show how each material responds in comparison to natural grass. The EPP underlayment material curve from Curve 2 shows similar hysteresis and stress/strain profile to a natural turf field from Curve 1. This is contrasted with the elastic response curve of the underlayment infills. made of cross-linked polyethylene foam, shown in curve 4, which does not exhibit the same hysteresis and time lag in the associated recovery and damping response of the material to racing loads.

The design of the global artificial turf system 10 establishes the deflection under running loads, the shock absorption under impact loads, the shape of the deceleration curve for an impact event, and the rebound and roll performance of the ball. These features can be designed to be used over time as the field ages and the infill becomes more compact, making the turf layer more rigid.

Panels 30 are designed with optimal panel compression characteristics. The entire shape of the panel is designed to provide bending rigidity so that the panel does not flex excessively when a vehicle passes over it while the panel is on the ground. This also helps to distribute the vehicle load over a large area of the substrate so that the contour of the subfloor foundation layer 16 is not disturbed. If the contour of the foundation layer 16 is not maintained, water will pool in areas of the field instead of draining properly.

In one embodiment of the invention, an artificial turf system for a soccer field is provided. First, performance design parameters for the soccer field are determined, related to a system energy absorption level for the entire artificial turf system. These performance design parameters are consistent with the FIFA (International Federation of Association Soccer) quality concept for artificial turf, the International Artificial Turf Standard (IATS) and the European standard EN15330. Typical levels of shock, or foot impact energy, absorption and deformation for these systems are within the range of 55-70% for shock absorption and about 5 to about 11 millimeters for deformation, when subjected to tested with Advanced Artificial Athlete (EN14808, EN14809). The vertical bounce of the ball is from about 60 centimeters to about 100 centimeters (EN 12235), the vertical permeability to water is greater than 180 mm/h (EN 12616) along with other standards. Other performance criteria may not be directly affected by the performance of the subfloor, but may be affected by the overall design of the turf system. The overall design of the turf system, including subfloor interactions, may include surface interaction such as resistance to rotation, ball bounce, slip resistance, and the like. In this example of designing a soccer field, a performance level for the entire artificial turf system of a specific standard is selected. Next, the assembly of the artificial grass is designed. The selected underlayment performance characteristics will be complementary to the overall turf performance characteristics to provide the desired overall system response to meet the desired sports performance standard. It is understood that the steps of the above example can be performed in a different order to produce the desired response from the system.

In general, the design of the turf system having a complementary subfloor 14 and a turf assembly 12 with performance characteristics can, for example, provide a turf assembly 12 that has a low amount of shock absorption and an underlayment layer 14 that has a high amount of shock absorption. By setting the relative supplementary performance characteristics, many options are available for turf design, such as turf height, knot density, yarn type, yarn quality, infill depth, infill type , backing and lining. For example, in prior art infill systems, one option would be to select an altered and/or shallow ratio of sand to rubber infill, or the use of an alternative infill material in the turf assembly. If in this example the performance of the turf assembly has a relatively low specific shock absorption value, the shock absorption of the underlayment will have a relatively high specific value. In one embodiment, the filler material 24 having the wood particles 24b as the top layer and the sand 24a as the bottom layer provides a generally low shock absorption value for transferring impact loads to the subfloor layer. The infill material 24 having the top layer of wood particles 24b also dampens the restitution or recovery response of the turf assembly to provide a firmer footing feel for the athlete, particularly during running.

As another example having different system characteristics, an artificial turf system for American football or rugby can provide a turf assembly that has a high amount of energy absorption, while providing the underlayment with low energy performance. energy absorption. When establishing the relative supplementary energy absorption characteristics, the selection of a large depth of infill material in the turf assembly can be considered. Also, when the energy absorption of the turf assembly has a value greater than a specified value, the energy absorption of the underlayment will have a value less than the specified value.

A sports field with dense, uniform, smooth and healthy natural grass provides familiar and familiar characteristics by which sports equipment, playing tactics and playing rules have been developed over time for this form of playing surface in the outdoor field sports. A thick, consistent, and soft turf provides a benchmark for quality and safety of play, and serves as a benchmark for stable athlete footing, cushioning levels (energy dissipation) in falls, slips, or tackles. , and heat transfer (cool) the playing surface in hot weather. Although relatively firm under the load of an adult running athlete, natural grass surfaces can absorb a high degree of impact force through a combination of particle displacement and crushing of the natural materials. Research evidence has shown that, while firm underfoot, a high-performance natural turf can significantly reduce the risk of head or body injury by effectively dissipating impact energy charges. The infill material 24 having the wood particles 24b provides particle displacement and particle deformation that mimics the natural turf field. As will be explained below, the wood particles 24b have a grain structure oriented generally along a longest dimension of the particle to provide desired deflection of the particles along with water absorption.

The sand is commonly used to build systems into the root zones of natural turf for high performance sports. Sand is chosen as the main construction material for two basic properties, resistance to compaction and better drainage/aeration status. Sands are more resistant to compaction than finer earth materials when used within a wide range of soil moisture conditions. Clay soil can provide a more stable surface and an improved growing medium compared to sand. But, under normal or optimal conditions, clayey soil will quickly compact and deteriorate if used during periods of excessive soil moisture, such as during or after a rainy season. A properly constructed sand-based natural grass root zone, on the other hand, will resist compaction even during wet periods. Even when compacted, sands will retain better drainage and aeration status compared to native soil root zones with the same level of traffic. Sand without vegetation, by itself, is not intrinsically stable; therefore, it is advantageous to use grasses with superior wear tolerance and recovery potential to withstand heavy foot traffic and high shear forces. However, sand has an incredible load-bearing capacity; and if a dense and uniform turf cover is maintained, the sand-based system can provide a very stable, firm, smooth, safe and even playing surface. A successful sand-based root zone system depends on the proper selection of materials. Proper selection and grading of sand, organic amendment, grass species and gravel underlayment are critical to the performance of the natural sports turf surface.

A commonly used reference standard for the construction of a high-performance sports turf rootzone is ASTM F2396, "Standard Guide for Construction of High-Performance Sand-Based Rootzones on Sports Fields." This specification describes a natural turf root zone consisting of approximately 95% graded sand and approximately 5% organic materials (eg, peat) by weight. Another commonly used standard for the construction of a performance sports turf rootzone is the USGA Specification Sand Rootzone Construction Guide. This specification describes a natural turf root zone consisting of at least 90% graded sand and no more than about 10% organic material (eg, peat) by weight.

To address the problems with the current third generation synthetic turf system, the infill material 24 of the present invention provides an improved natural infill composition modeled after the performance of high quality natural sports turf. Compared to other organic infill systems or synthetic infill materials, the infill composition of the infill material or layer 24 produces a cooler temperature playing surface in hot weather conditions over an extended period of time. Compared to other organic fill systems, the increased amount of water retention within the system allows for prolonged exposure to heat before retained moisture is fully evaporated. Given the similarity to the performance of a natural sports turf, the various embodiments of turf systems incorporating the infill described herein provide the traction and grip of natural turf. The fill material is biodegradable unlike the disposal of synthetic material waste in landfills. A shock absorbing underlayment prevents excessive compaction of the fill to maintain consistent performance properties over the life of the field.

Infill material 24 is packed between synthetic turf fibers creating ballast, firmness, stability and traction. The energy transferred through the infill material 24 is absorbed by a resilient underlayment base to provide shock absorption properties comparable to a performance sports turf rootzone, as shown in Figure 3. Examples of a suitable resilient underlayment or underlayment for synthetic turf sports fields are well known, such as the underlayment materials available from Brock International, Boulder, Colorado. The use of a resilient underlayment helps prevent excessive compaction of the particle fill.

Sand can be defined as a naturally occurring granular material composed of finely divided rock and mineral particles. Sand 24a, for use as a component of fill 24, is defined as one or more of the following: Silica sand, silica quartz sand, rounded grained silica quartz sand, washed sand, and grained silica quartz. rounded and washed and graded round grained silica quartz sand, and zeolite. In one embodiment, the sand particles 24a have a diameter within the range of about 0.0625 mm (or 1/16 mm) to about 2.0 mm. Optionally, the sand 24a can be colored.

The organic component of the filler is wood particles 24b and is composed of heartwood particles and sapwood portions of hardwood or softwood trees, as will be described below.

In one embodiment, the fill material 24 includes sand 24a in an amount within the range of about 70 to about 98 percent by volume dry weight, and wood particles 24b in an amount within the range of about 2 to about 30 percent by volume of dry weight. The sand 24a and wood particles 24b may be layered on the turf, with the sand layer 24a at the bottom. Alternatively, the sand 24a and the wood particles 24b can be combined as a mixture. Depending on certain factors, such as the location of the field (indoor or outdoor), the latitude, the amount of rain or the irrigation intervals, the exposure to solar load and the type of sport or use, the field adapts to other realizations. of the filler material 24 may be about 10 percent wood particles 24b and about 90 percent sand 24a by weight. In other embodiments, there may be a higher proportion of sand 24a, including up to about 95 percent by weight or about 75 percent by volume. For example, in regions that receive large amounts of rainfall and generally have cooler ambient temperatures, fewer 24b wood particles can be used as a percentage of the total fill, since the playing field does not reach high temperatures that require evaporative cooling from the stuffed. Similarly, indoor playing fields typically do not receive direct sunlight and have moderate ambient temperatures, thus requiring fewer wood particles in infill. Conversely, in lower latitudes and regions that experience more sunny days and higher ambient temperatures, a higher proportion of wood particles in the infill would allow the turf system to absorb more water during irrigation or rain. and would therefore provide evaporative cooling of the playing surface for an extended period of time. In one embodiment, the amount of sand 24a applied with filler 24 constitutes approximately 144 N/m2 (3 pounds per square foot). In other embodiments, the amount of sand 24a is within the range of about 239 to 383 N/m2 (5 to about 8 pounds per square foot). In a particular embodiment, the amount of sand 24a is approximately 287 N/m2 (6 pounds per square foot). The weight of the sand helps support the turf and subfloor.

By way of example, the thickness of the filler 24, shown in Figure 3 as zone AA, may be a layered structure of sand 24a and wood particles 24b. In general, a thicker layer of wood particles and a thinner layer of sand improve field drainage and the field's ability to provide longer periods of evaporative cooling in hot weather. The field also has higher shock absorption due to the mobility of more wood particles (than in a thin wood layer infill). In hot climate regions, a 2:1 ratio of sand to wood particles (by weight) provides excellent performance for a top-level soccer field. A high quality general purpose field may have a ratio of sand to wood particles of 4:1 (by weight). A general purpose field in humid regions may have a 5:1 sand to wood particle ratio.

As shown in Figure 13, the wood particles 24b are generally elongated and have a length L; a width, W; and a thickness, T The length, L is in the direction of the grain structure, G of the trunk from which the particles are formed, as shown in Figure 12. The length of the particles of the wood component 24b may be within the range of about 1.0 mm to about 10 mm. In a preferred embodiment, the length of the particles may be in a range from about 1.0 mm to about 5 mm. A wood particle aspect ratio is the ratio of particle length, L, to particle width, W, or thickness, T. The aspect ratio ranges from 4:1 to 10:1 . The dimensions of width, W and thickness, T may be in a ratio of approximately 1:1 to 5:1 and are preferably within a range of approximately 1:1 to 1.5:1.

Sand/Wood Infill 24 also mimics the performance, safety, and drainage properties of a sand-based natural grass root zone. The wood component of the infill material 24 improves traction and overall player-surface interaction relative to a sand-only infill or a synthetic sand-infill material. Sand/Wood Particle Infill 24 provides consistent performance and safety results between dry and wet conditions as determined by ASTM F355, ASTM Fl292, and EN 14808 and EN 14809. Sand/Wood Infill also provides a surface with energy restoration comparable to pristine natural sports turf.

In one embodiment, the sand/organic infill provides the turf system with a nature that mimics natural grass. The infill 24 is not as resilient as that provided by conventional sand/rubber ground artificial turf infill systems, but it does provide a superior and more natural footfall response to users of the turf system. Users are more likely to perceive that they are running on a field that is very similar to a natural grass field. Therefore, the padding material is relatively low resilient and does not act as a primary shock absorbing layer but as a load transfer layer. This load transfer management system relies primarily on the subfloor layer for resiliency and shock attenuation characteristics. Figures 2 and 3 represent comparative schematic illustrations showing various zones of deflection and load transfer of prior art systems (Figure 2) and the embodiments of the turf system described herein (Figure 3). A comparison of the deflection level of the padding in the padding zone A of Figure 2 shows more deformation under load, giving more shock absorption within the layer, but subsequently less load transfer to the layer of subfloor, zone B. Infill zone AA in Figure 3 illustrates the effect of load transfer to the zone BB subfloor layer, which deforms under applied load more than prior art subfloor layers.

The sand/organic infill 24 provides a relatively fast drainage system, faster than would be expected with a natural turf system. However, the organic component of wood particles 24b has a water retention capacity that allows the turf system to dry out slowly once it gets wet. This look more closely mimics a natural turf system than a conventional sand/rubber ground artificial turf system. The composition of sand and organic fill allows a controlled percentage of water to be retained in the fill for some time without the detrimental effect of premature rotting.

As described above, organic fill material may include a mixture of sand and organic material or may be applied in layers to the site of the turf field being constructed. Application of the infill mixture or the individual components to the turf can be done by a drop spreader or a broadcast spreader, or by any other suitable mechanism.

The organic material used in padding 24 can include any of the organic materials described above, such as bamboo and cypress, hardwoods such as poplar, and softwoods such as pine and cedar. In a preferred embodiment, the wood particles 24b are composed of frankincense pine. The infill 24 may also include other organic materials such as coconut shell, rice husk, and cork materials as fillers or inorganic materials such as perlite or vermiculite to adjust the specific performance characteristics of the turf.

In some embodiments, the organic portion, including the wood particles 24b, of the infill 24 is designed to mimic the ground cover of natural grass. Vegetative cover on natural turf provides excellent traction and resistance to the rotation involved in the rotation of a cleat in an athlete's shoe. The international soccer body, FIFA, has a foot roll range test to measure the resistance to rotation in the roll of an athlete's shoe. In one embodiment, the artificial turf using the organic infill 24 has a resistance to rotation of at least 25 Nm (meters per newton) and not more than 50 Nm according to appropriate FIFA tests, the Rotational Resistance Test FIFA 10/05-01 and FIFA 06/05-01. Too little resistance to rotation means that the surface is unstable to walk on. Too much resistance to rotation means that the foot or cleats cannot pivot on the surface (also known as cleat lock), increasing the risk of lower extremity injury. In some of these embodiments, the organic materials used in the filler 24, along with the wood particles 24b, may also include organic fibrous material, such as hemp, flax, grass, straw, wood pulp, and cotton fibers. In other embodiments, synthetic fibrous materials such as polyethylene may be used.

In certain embodiments, the organic component of the filler 24 is composed of wood particles 24b of different sizes. Smaller particles intermingle with larger particles, and different particle sizes tend to produce a good filler mix, both from a stability and durability standpoint.

The packing 24 may be subject to sedimentation, separation, and segregation over time. Various strategies can be used to prevent or delay separation or segregation. In some embodiments, various additives, such as starch or adhesives, or cohesion-enhancing substances or coatings, or polymer emulsions, are used to cause the filler particles, including the wood particles 24b, to stick together and to prevent or retard the particles in the infill 24 from segregating by size during storage, transportation, and application to the turf field, and also while the turf field is in use after installation. Ideally, the filler particles 24b have an affinity for each other, both physically and chemically. Physically, the particles 24b can form a lattice, randomly orienting the length L of the particles in various directions. Chemically, the 24b particles have an attraction as a result of weak particle-to-particle hydrogen bonding.

It is also advantageous to employ a mechanism to prevent over-compacting of the filler 24. A mechanism that can be used to prevent size segregation and to prevent over-compacting is to use particles of different shapes, i.e. some of the filler particles have one shape. or set of shapes and other filler particles have other shapes. Other mechanisms can be used to prevent overcompaction. Furthermore, having a particle size distribution of the filler particles will improve the resistance to rotation of the cleats of athletes' shoes. It is desirable to provide an infill that acts as a ground cover area on natural turf for the rotation of shoe cleats. In one embodiment, a topcoat layer, other than the subfloor fill mix, is applied as the top fill layer during construction of the turf system.

Conventional turf systems using a sand/rubber ground infill mixture tend to absorb heat, and such systems often experience uncomfortably hot turf surface temperatures during hot sunny weather. One of the favorable attributes of a turf system using the organic infill 24 is that the infill, and in particular the wood particles 24b, will have a natural tendency to act as a moisture reservoir, particularly depending on their size and ratio. aspect compared to grain orientation. As moisture is added to the turf, the organic material absorbs the moisture. Later, the moisture evaporates from the infill 24, thus providing a cooling effect on the turf system. Said cooling effect is very advantageous for the turf system exposed to hot climates. The field can be cooled by applying water to the field. Ideally, the turf field is designed to release its moisture slowly so that the cooling effect occurs over a longer period of time. Various physical aspects of the filler 24, and in particular the wood particles 24b, will affect the amount of moisture the filler can absorb and the rate at which the moisture is absorbed, and will also affect the rate of evaporative cooling during moisture release. moisture during a drying process. The surface area of the particles 24b in the packing 24 will affect the amount of moisture that can be absorbed and adsorbed, with higher moisture content being adsorbed with particles having a larger surface area. The use of other fibrous materials can also favorably affect the absorption qualities of the sand/organic filler 24. In addition, an additive, such as a wetting agent, may be incorporated into the filler mixture. Other examples include the use of vermiculate, perlite and zeolite, as well as other organic and inorganic absorbents including montmorillonite and bentonite clay. These materials act as a water reservoir by absorbing moisture. In one embodiment, the additive will make the fill mixture more hydrophilic. A wetting agent is particularly useful for improving the wetting of the fill mix when it is first exposed to moisture. One or more of the fillers listed above can act as a filtering agent as well as a hydrating agent. The sand/wood fill does not leach harmful chemicals, toxins or impurities.

The geometry, size and orientation of the grain of the wood particles 24b aid in the absorption and release of water while maintaining the resistance of the particles to degradation from applied loads and maintaining the desired load transfer characteristics on the surface. layer 14 subfloor. As the particles 24b absorb water, the water migrates very rapidly along the grain boundaries of the cellulose fiber and into the lignin and xylem. Due to the size and aspect ratio of the particles 24b, water is absorbed rapidly, rapidly increasing the density of the particles to prevent the particles from floating from the fill 24 during and after rain or irrigation cycles. The rapid absorption is due to the large specific surface area of the particles and the orientation of the veins along the particle 24b. This water absorption characteristic affects the performance properties of the infill 24 and the overall turf assembly 12 . As the particles absorb water, the coefficient of friction between adjacent particles 24b in the packing 24 decreases. This allows the particles to move more easily past each other. Wet particles resist fracture, but also have reduced mechanical properties, such as strength and flexure. While the expectation would be that a reduced coefficient of friction would produce a slippery surface on artificial turf, the particles improved elasticity and reduced mechanical properties allow for particle-to-particle mechanical interactions from changes in geometric shape (such as consequence of aspect ratio and size range) that compensate for the lower friction values. This is possible because the cellulose fibers, although separable along the grain boundaries, are in substantially high tension. If the vein boundaries were oriented randomly or substantially along the short dimensions (W or T), the particles would fracture to a size similar to that of sand or ground rubber. So they would become more like greased ball bearings rather than slightly interlocked or bent rods.

A particular benefit of increasing the moisture absorbing capacity of the organic fill 24 is that in water-scarce geographic locations the amount of water needed to keep a cooling system cool will be minimized. grass that has an organic infill 24. When designing an artificial turf system that will use an organic infill 24, the amount of solar loading and expected ambient temperatures can be taken into account to provide an adequate amount of evaporative cooling for a comfortable sports playing surface.

In a particular embodiment, a system is provided for designing turf systems, where the amount of solar loading and expected ambient temperatures are taken into account to provide an adequate amount of moisture-containing organic material to maintain hydration at the location of the system. of lawn. Designs for turf systems located in drier, sunnier locations will be provided with an infill mix with a higher amount of moisture retaining materials than the infill mix for turf systems located in higher moisture locations. Also, infill mixes for drier, sunnier locations will be designed with an infill mix that has a slower water release rate than the infill mix for turf systems in wetter climates. In this way, the turf system will adjust itself to accommodate the prevailing humidity level expected at the design location.

Other additives can be applied or incorporated into the filler mix to achieve additional benefits. An additive is an odor control substance in artificial turf applications for pet surfaces, such as outdoor artificial turf pet mats. Such mats are known as landscape turf. Additives can be used to treat organic fill material to retard or prevent decomposition. In addition, the filler mix can be treated with antimicrobial agents to prevent the growth of undesirable organic substances. For example, quaternary ammonium compounds can be used not only to provide antimicrobial protection, but also as an antistatic agent to prevent wood particles from adhering to athletes' clothing.

It can be seen that the artificial turf system having an organic infill 24 can provide a number of advantages. One particular advantage is that the materials will be easier to recycle than artificial turf systems that use ground rubber. Another advantage is that the composition of the infill 24 can be adjusted to meet the particular requirements of any particular artificial turf installation. For example, the infill composition 24 can be designed to provide the best possible walking surface for a particular artificial turf application, such as the development of a football turf surface, or a turf surface for a soccer field. would have different footing and rebound (recovery) requirements than on a football field. Independently, the underlayment layer, such as a foam underlayment, can be constructed to provide the proper impact response in the specific turf application. Therefore, an artificial turf system designed to meet the requirements of any particular application can be built.

In one embodiment, the padding 24, which can absorb moisture, has been applied with an environmentally friendly antifreeze composition to prevent the padding 24 from freezing on a football field during subzero temperatures. An example of such material is disclosed in US-A-7,169,321.

In another aspect, the concept of maintaining the hydration of the organic filler material is incorporated into the filler material. Organic fill is typically a mixture of fine wood, bark, and wood by-product particles and may include ground coconut shells, cork, and coconut fiber to produce a free-flowing material that, when placed on sand and worked in Artificial turf fibers help provide a playing surface that offers athletes the traction and, to some extent, the feel of natural grass. But today's commercial organic fillers require a certain amount of moisture to help them maintain those characteristics. The finest wood particles absorb and release moisture easily, helping to give the filler the desired feel. The evaporative cooling of the infill prevents the playing surface from heating up as much as synthetic turf fields that have incorporated an infill material of sand and ground rubber. But because the size of the organic particles is small (typically much less than a millimeter in diameter), the evaporation of moisture from inside the particles is relatively rapid, so the cooling effect provided by the filler is brief. ; on the order of a few hours after moisture is applied, and is not a practical means of cooling the field for athletic play. Also, after the moisture evaporates, the ingredients in most organic fillers become friable and pulverized due to the sporting activities that take place in them. The padding loses its resilience and compacts, making the playing surface harder and less able to provide traction for athletes.

While we do not wish to be bound by theory, research and testing have shown that the sand base applied to synthetic turf below the infill is the component that limits the rate of vertical drainage of water through the turf system, regardless of the fill material on the sand. But with typical organic fills, fine particles that seep into the sand layer fill the voids between the sand granules, further impeding water flow during rain events. During heavy rains, the field may not be able to filter all the water through the fill and turf, causing "ponds" and surface runoff that can wash the fill to the edges.

In another aspect of the present invention, the filler combines wood particles from various tree species, and the particles have a certain geometry that prevents them from becoming friable and breaking when subjected to the shearing action of sports games.

The wood particles described in the present invention are coarse enough to allow water permeation during heavy rain and since they are resistant to mechanical breakdown, they do not form a layer of fines that can impede the flow of water through the layer. filler. There are also no significant fines that get trapped between the grains of the sand layer.

Another configuration of the present invention considers a systems approach using a layer of coarse sand along with organic fill components to maximize water drainage through the sand and reduce the possibility of fine particles getting into the sand. the voids between the grains of sand.

Wood particles are composed of the heartwood and sapwood of softer woods such as southern yellow pine and western red cedar, which are considered ideal due to their relative abundance and renewability of resources. But functionally hard woods such as poplar can also be used. Unlike other organic infills that can include significant amounts of bark and partially decomposed wood particles that can be easily disintegrated by mechanical shearing, the wood chip component of the inventive infill is resistant to the abrasion found in other sports surfaces. artificial, including those based on coconut shell or rubber-based fillers. Also, the particles are not as hard as other organic materials like ground walnut shells, so they don't have the same abrasive feel against the skin. The hardness of wood is measured by the Janka hardness test. Softwoods like southern yellow pine have a Janka hardness of between 700 and 900, while poplar has a Janka hardness of 1100 to 1300. Walnut shells cannot be measured in a Janka test, but they are so hard that they have been characterized on the Moh's hardness scale for minerals to be between 3 and 4. In addition to their hardness, walnut shells have sharper angular edges than processed wood particles, which increases their abrasiveness.

The wood particles 24b can have a range of sizes from 1mm x 1mm to 5mm x 5mm in cross section and up to 20mm in length. In a preferred embodiment, the wood particles 24b may have a size range of 1-2mm x 1-2mm in cross section and 1-5mm in length. The edges of the particles may be well defined as a result of the chipping and grinding operations used to produce them, or they may be rounded as a result of the heavy abrasion that takes place during wood processing. The tree bark layer is an undesirable component of wood particles due to its friability, but is acceptable in amounts up to 10%.

The wood particles 24b can be sized for specific applications, such as the sport to be played and the playing conditions. For example, a soccer field will benefit from wood particles 24b that range in length from about 3mm to about 7mm. The width and thickness can be between 1.0mm and 2.0mm. The longer particles allow athletes' cleats to grip as they run quickly and change direction slightly, but when they pivot, shear forces on the particles cause them to shift and move, similar to how they loosens a natural turf under torsion loads. This loading scenario is common in soccer game. On a football field, the length can be between more than about 2 mm and less than about 6 mm. The width and thickness can be between 1.0mm and 2.0mm. In soccer, the particle size distribution is slightly narrower to give the padding a bit more mobility and to prevent studs from binding under very high player-to-player impact forces. In a general purpose athletic field covering a wide range of sports and activities, the length of the wood particles can be between greater than about 1 mm and less than about 5 mm. The width and thickness can be between 1.0 and 2.0 mm. The narrower particle size range creates a firm field for flats and cleats. Higher load transfer to shock absorbing padding with livelier ball bounce results in a good playing surface for children's activities and sports such as lacrosse.

As a tree grows, the cambium generates mainly longitudinal cells whose lengths are about 100 times longer than their widths. Longitudinal cell walls form the grain that is visible as long parallel lines in the wood particles. In one filler configuration, the wood particles are manufactured such that the wood particles are elongated, have one longest dimension, and the wood grain is oriented in the longest dimension of the particle, as shown in the drawing of a single elongated particle of wood. In this configuration, the particles are less susceptible to fracture when impact, bending or shear forces are applied to the fill, such as during sporting activity.

The wood particles of the present invention are large enough to absorb moisture within the particles from rain or irrigation, and slowly release the moisture over a period of up to two days. Figure 16 is a table showing a comparison of turf surface temperatures before and after water was applied to plain synthetic turf without infill, synthetic turf filled with sand and rubber, and synthetic turf filled with sand and wood chips. of the present invention. The cooling effect of moisture dissipated quickly on plain, rubber-filled turf, since the applied moisture was only on the surface of those materials. But the wood particles continued to provide evaporative cooling for 48 hours, making it a practical means of cooling a sports playing field. The repetitive application of water and subsequent evaporation does not affect the durability of the wood particle filler.

The preferred particle sizes and size distribution provide various functions as an infill for synthetic turf. The more cubical particles provide bulk to the infill layer and have limited mobility to fill large voids in the infill once it is applied to the turf and thus help stabilize the infill layer. Particles that have higher aspect ratio shapes can "bind" or interlock to a limited degree, providing superior traction for athletes running on the field compared to infill materials that have more cubical particle shapes. or spherical.

Elongated wood particles, as described above, can also help prevent the padding from compressing as a result of prolonged play. Depending on how the elongated particles are supported from below, they can, when a vertical load is applied to the turf, act as small springboards or bent bars that deflect under load and return to their original shape and position when the load is relieved. Although the particles themselves are not resilient, the ability of the elongated particles to flex under load and recover provides a slight resilient feel during athletic activity, much like a groundcover area on natural turf has a slight resilient feel. of resilience. This recovery of shape also helps prevent compaction of the infill layer and maintains its ability to drain water vertically through the turf.

Although cellulose and lignin, the main organic components of wood, have specific gravity greater than 1.0, the specific gravity of dry wood is much less than 1.0 due to air displacing water in the wood when it dries. Therefore, dry wood easily floats on water. But over time, the water is absorbed by the cellulose in the wood and once the air moves inside the wood, the wood sinks. The time required for the wood to sink in the water is, in part, a function of the ratio of the surface area to the volume of the wood. Smaller particles have a higher surface area to volume ratio than larger chips or logs, and they absorb water more quickly. The wood filler particles of the present invention have surface area to volume ratios as high as 6 mm -1 up to about 0.75 mm -1 . The wood particles of the present invention sink in water in as little as two seconds.

Although designed specifically for sports turf performance discussed above, wood particles have the added and unexpected benefit to sports field owners of being less prone to being washed away during heavy rain than other, more buoyant organic infills. As the rain begins to fall on the wood-filled turf, the water is rapidly absorbed by the small wood particles, increasing the specific gravity of the particles to more than that of water. If the instantaneous rate of rainfall exceeds the system's ability to drain water vertically and laterally through and under the turf, water can pool and begin to drain through the turf surface. Water easily washes away the floating fill and accumulates along the field margins, requiring costly and time-consuming replacement of the fill before the field can be used again. The wood particle filler of the present invention, which has absorbed water so that the wood particles become denser than water, is not washed away by the accumulation and surface drainage of water in a severe storm.

The rapid absorption of water by the wood particles 24b does not compromise the slow evaporation of water and the resulting cooling effect when the particles dry. In the same way that a cellulose sponge absorbs water quickly but takes a long time to dry, the tortuous path that water must take from within the wood particles plus the forces of attraction between the water molecules and the cellulose in the wood slow down the rate of evaporation of water from the fill.

Some organic fillers are made up of very small (<< 1 mm3) cellulose-based particles including, for example, ground coconut shells. These particles absorb water very quickly, but because the surface area to volume ratio is so high, the moisture evaporates quickly and the cooling effect is short-lived. As discussed above, these dry particles are friable and are easily pulverized by athletic activity, rendering them useless as filler.

Cork is another organic infill material that is sometimes used as a replacement for rubber infill in artificial turf sports fields and consists of ground particles that have a high surface area to volume ratio. But cork is a chemically and physically unique organic material that is different from the physical and structural constitution of the filler material 24b, particularly related to the shape and structure of the resulting processed particles. About 50% of the air spaces in cork are completely enclosed within the cork matrix, making it resilient, but extremely difficult to displace air with water. In addition to cellulose and lignin, which are hydrophilic, the cork matrix contains a lipid molecule called suberin, which is hydrophobic and resists gas permeation. The physical structure of the cork cells and the presence of suberin may make cork an ideal material for sealing wine in a bottle, but make the cork filler buoyant and susceptible to floating in heavy rain.

Any suitable method can be used to create elongated wood filler particles having the wood grain oriented in the longest dimension. Optionally, one procedure that can be used is to cut or "chip" wood chips or discs from a tree or piece of wood using a wood chipper, with the cut across the grain using a cutting disc, as shown in Figure 14, or a cutting drum as shown. shown in Figure 15. The resulting pieces of wood will have the grain orientation in the direction of the thickness of the disc. The linear speed of the wood being fed into the chipper is controlled in relation to the speed of the cutting disc or drum, so that the length of the cut wood discs is kept between about 1.0 mm and about 6.0 mm. The wooden discs are then broken into wood particles by any suitable process. Optionally, one method of breaking the chips is to use a hammer mill, in which the hammers break the chips along the grain. Next, the broken wood chips are centrifugally forced through a metal screen having a plurality of holes of a certain diameter, and the resulting wood particles will have the wood grain mainly oriented in the elongated direction of the particle. In one embodiment, at least about 60 percent of the elongated particles will have the wood grain oriented in the elongated direction of the particle. In another embodiment, at least about 70 percent of the elongated particles will have the wood grain oriented in the elongated direction of the particle. In yet another embodiment, at least about 80 percent of the elongated particles will have the wood grain oriented in the elongated direction of the particle. With this procedure, controlling the thickness of the wood chips produced by the chipper is critical to making filler wood particles with the correct size, size distribution, and grain orientation. The logs are fed into the chipper by hydraulically driven feed rolls that can be controlled to provide a stable feed rate so that the chipper disc or drum runs at a nearly constant speed. The thickness of the splinter can thus be kept between one and six millimeters. The wood chips are processed through a hammer mill, which breaks the chips by cutting them along the grain boundaries. The speed of rotation of the hammers and the size of the opening in the sieves control the cross-sectional area of the wood particles, which preferably range from one square millimeter to nine square millimeters. If the size or diameter of the screen is too large, the residence time of the wood particles in the hammer mill is too short to break the chips to the preferred particle size. If the sieve size is too small, the chips can disintegrate too much so that the particle size distribution results in too many fine particles that cannot be used as filler.

While chipper and hammermill process conditions can be set to obtain preferred particle sizes, a certain percentage of particles are expected to be larger or smaller than that range. A mechanical screen is used to separate the larger and smaller particles of the preferred filler particles. Larger particles can be processed through the hammer mill a second time as part of the main feed line. The fine particles can be collected and sold as fuel pellet ingredients, for example.

Moisture content during processing also affects the size and size distribution of wood particles. Freshly cut logs retain approximately 50% moisture. When freshly cut logs are chipped, it is easier to maintain a chip-free log cut and chip thickness is easier to maintain. Fresh logs are less susceptible to splitting than dry logs when splintered. Fractured logs create long shards and chips that pass through the chipper. These fragments and chips are difficult to cut into preferred particle sizes in the hammer mill, resulting in either an excess of large particles that need to be reworked or a number of smaller chips and fragments that can give the filler a coarser feel. thick than desired. Dried logs also generate more fines or wood flour when chipped. Although wood flour has utility in alternative products such as fuel pellets, it is preferred that the percentage of filler wood particles be as high as possible.

After chipping the fresh logs, the wood chips can optionally be processed through the hammer mill immediately. The wet chips break after being struck by the hammers and pass through the screen. If the screen holes are relatively small in diameter, some of the wet wood particles can accumulate on the screens and over time cause a blockage in the screen openings, increasing the residence time of the particles in the crusher. The wet particles can be cut into fine, fibrous strands that are mechanically less durable than preferred particle sizes. To avoid screen blockage, a screen with larger diameter holes can be used or the chips can be fully or partially dried before crushing. The chips can be dried to a moisture content of 25-40% moisture before being crushed, or alternatively the chips can be dried to 10-25% moisture before being crushed.

Wood particles that have been processed through the crusher should preferably be dried to a moisture content of 15% or less before passing through a mechanical sieve. Alternatively, the wood particles can be dried to a moisture content of approximately 25% before being sized. Finished filler wood particles can be stored in a rain-protected storage facility or packaged in breathable bulk storage bags for immediate shipment and delivery to the customer.

It is virtually impossible to prevent long wood chips or fragments from being created during the wood chipping process. Even with subsequent crushing and sieving operations, some of the chips and fragments remain in the mix and give the particles the appearance of being abrasive and prone to punctures, tears, and fine slices in the skin.

To remove chips and shards, wood chips can be processed through a notch separator, which selectively separates chips and long shards from particles of desired length. Notch separators are commonly used to separate grass seed from weed seed in the turf industry. The particles to be separated are passed through the inner surface of a rotating steel cylinder shell having small hemispherical or other geometrically shaped depressions in the surface. Wood particles of the desired size and shape are captured in depressions or notches in the surface and transported upward as the cylinder rotates. At a certain position, the particles fall out of the depressions and collect in a channel placed approximately in the axial center of the cylinder. An auger in the flume transports the particles to a material handling system for further processing. Particles that are unacceptably long in length are not collected in the barrel grooves and are carried along the barrel and removed from the process.

Wood particles processed with wood chippers and hammer mills may have sharp or angular edges due to the way the chipper blades or mill hammers cut or split the wood. During athletic play on a synthetic field filled with those wood particles, an athlete can slide across the turf surface, and the edges of the wood particles can feel rough against the skin. To reduce the apparent roughness of infilled turf, the wood particles can optionally be processed to round the edges of the particles.

Wood particles that have been chipped, shredded, dried and screened can optionally be conveyed pneumatically through cyclonic dust handling equipment that has been modified to include rough internal surfaces and narrow air passages so that the particles They can hit the rough surfaces and abrade the angular surfaces and sharp edges of the particles. Fine wood dust released from wood particles can be collected in filter bags and stored for use as fuel in wood dust-fired processing kilns or alternative wood flour products such as fuel pellets.

Alternatively, the processed wood particles may be conveyed and tumbled through a drum containing deburring media consisting of, for example, stone, ceramic or metal shapes which strike the rotating wood particles, either flattening or abrading sharp or angular edges.

Another process for removing the rough edges and surfaces of the wood particles is to convey the chipped, dried, and shredded wood particles to a cylindrical internal mixer having a central rotating shaft with blades resembling the blades of a turbine that They project radially from the axis. The paddles have flat surfaces that agitate and displace the wood particles axially through the interior cavity of the mixer. As the particles collide with each other, the surfaces are slightly abraded, causing the edges of the particles to round slightly and the surfaces to become smoother.

Under certain processing conditions, the large wood particles that leach from the fill can be used as a soil additive in place of perlite, providing a revenue stream that is of higher value than other applications to farmers. by-products of the filling process. The wet wood chips can optionally be dried to a moisture content of 25-40% moisture, then processed in a hammer mill using a hammer rotation speed of, for example, 2000 rpm. A small hammer mill sieve size (eg, 0.250 inch diameter) may optionally be used. The large particles resulting from this process are generally cuboid in shape with square or slightly rectangular quadrilateral faces, and with edge dimensions of between five and seven millimeters.

Turf and infill wear resulting from athletic play on the surface can be simulated with a Lisport Classic meter. A pair of heavy, knurled rollers traverse an infilled turf sample in the forward and reverse directions for a prescribed number of cycles. The rollers are coupled with sprockets and chains to rotate at different angular velocities, introducing shear and penetration into the turf and infill, thus simulating the movement of athletic shoes. When the wood particle filler described in the invention is subjected to the Lisport test, the particles become slightly rounded due to wear, making them feel less abrasive than when first processed.

A chemical additive can be applied to freshly processed wood particles to make them feel smoother and less abrasive. In one embodiment, a mixture of glycerin and water can be added to the wood particles using any of several types of batch or continuous mixers so that the fluid is absorbed into the surfaces of the wood particles. The glycerin gives the particles a somewhat slippery surface that feels smooth to the touch. As infilled turf is subjected to sports use, rain and irrigation, surface glycerin is removed or dissolved from the particle surfaces. But in the meantime, the particles are mechanically abraded by athletic activity, and the filler maintains a soft, relatively non-abrasive feel.

Colorants can be added to wood particles to improve the aesthetics of the infill when working on turf. Naturally occurring pigments such as iron oxide can be used to enhance color without the use of potentially harmful ingredients.

In an alternative infill configuration, wood particles configured as interlocking additive particles from the same trees as previously described, but with a cross-sectional area of approximately 1 square millimeter and a length to width ratio of up to 10 :1 or 15:1 can be mixed with the wood chips described above to form a network of interlocking particles that help prevent wood particles from being washed away by heavy rain. The interlocking particles also provide stability and traction for athletes whose cleats initially grip the interlocking particles, but then release with a nominal amount of torque energy.

The present invention also considers the complete turf system to solve the problems of compaction of organic infills and poor water drainage seen in organic infill fields. Some organic infills are not very resilient, particularly if the playing surfaces on which they are installed are not well maintained. The field of play can become difficult over time, increasing the risk of injury to players. Therefore, one configuration incorporates shock-absorbing expanded polypropylene padding beneath the synthetic turf to provide a firm footing for athlete performance while running, but superior impact attenuation to help reduce the potential for injury to the foot. head and body.

In another turf system, the various combinations of organic fills described above are placed over a layer of coarse sand having average grain diameters ranging from 1.0 to 2.5 mm, or about the same as the cross-sectional area of the wood particles in the organic filler. The size of the sand grains helps facilitate vertical drainage of water compared to typical sand layers where the grains are less than 1.0 mm in diameter.

In another turf system, the previously described organic infills, coarse sand, and EPP underlayment are combined with a synthetic turf that has a means to drain water through the turf and turf backing.

Claims (14)

1. An infill material (24) for an artificial grass system (5) comprising: a plurality of wood particles (24b), each particle defining a length dimension greater than a width or thickness dimension, each particle length dimension being oriented generally parallel to a grain structure of each particle, the length dimension in a range from about 1 mm to about 10 mm, the length and one of the width or thickness dimensions define an aspect ratio within a range from 4:1 to 10:1, each particle having a property water absorption that allows the particle to retain water and release it over time to disperse heat from the filler material (24), characterized by The wood particles (24b) are processed by tumbling or grinding to round the edges of the wood particles (24b) so that the edges of the wood particles (24b) are smoothed in comparison with a cut surface having a shape angular and sharp edge. The filler material (24) of claim 1, wherein the plurality of wood particles (24b) are formed from at least one of a heartwood or sapwood component of a hardwood or softwood species. and having width to thickness dimensions in a range of about 1mm to 2mm x 1mm to 2mm defining a cross section and the length dimension in a range of about 1mm to about 5mm, wherein the wood particles (24b) have a hardness measured on a Janka scale within a range of about 690 to about 1100. The filler material (24) of claim 1 wherein a) the length of the wood particles is between more than 3 mm and less than 7 mm; O well; b) the length of the wood particles is between more than 1 mm and less than 5 mm. The filler material (24) of claim 1, in a first alternative that further includes sand (24a) in which the plurality of wood particles (24b) and sand (24a) are combined as a mixture, the mixture configured to be deposited on a carpet (12A) of artificial grass; in a second alternative further including sand (24a) and wherein the plurality of wood particles (24b) are combined with interlocking additive particles having a cross-sectional area of approximately 1 square millimeter and a length to length ratio width within the range of about 10:1 to about 15:1 and wherein the sand (24a) has an average grain diameter in the range of about 1.0 mm to about 2.5 mm; O well wherein in a third alternative, the plurality of wood particles (24b) are coated with at least one of an antimicrobial agent, a wetting agent, and an antistatic agent. 5. A set (12) of artificial grass comprising: a grass mat (12A) having a plurality of separate synthetic grass blades (20); and an infill material (24) according to claim 1 dispersed on the turf mat (12A) between the turf blades (20), the infill material (24) further including sand (24a). The artificial turf assembly (12) of claim 5, wherein the infill material (24) further includes sand (24a), wherein the plurality of wood particles (24b) form a first layer and the sand (24a) forms a second layer such that a ratio between the weight of the second layer and the first layer is in at least one of a range of approximately 2:1, 4:1 or 5:1. The artificial turf assembly (12) of claim 5 or 6, wherein the turf mat (12A) includes a backing layer (22) to which separate synthetic turf blades (20) are attached, The infill material (24) is dispersed over the turf mat (12A) in layers in which a first layer is formed from the sand (24a) in a depth range of approximately 10mm to approximately 20mm and a The second layer is dispersed over the first layer and comprises the plurality of wood particles (24b) in a depth range of about 10mm to about 25mm. The artificial turf assembly (12) of claim 5 or 6 including a layer (14) of underlayment. The artificial turf assembly (12) of claim 8, wherein the infill material (24) defines a first spring rate of the artificial turf assembly (12) and the underlayment layer (14) defines a second spring rate. spring constant which is of lesser magnitude than the first spring constant such that the applied loads on the artificial turf assembly (12) are substantially transferred to the subfloor layer (14) and the second spring constant provides the majority of of a reactive response load through the artificial turf assembly (12) against the applied load. The artificial turf assembly (12) of claim 9, wherein (i) Underlayment layer (14) is an expanded polyethylene or polypropylene foam bead material having a core and a plurality of projections extending from the core and in contact with a backing layer (22) of the grass mat (12A), the plurality of projections defining the second spring constant and the core defining a third spring constant that is greater than the second spring constant and equal to or less than the first spring constant, (ii) the length of the wood particles is between more than 3 mm and less than 7 mm and in which the ratio between the weight of the sand (24a) and the wood particles is between 2:1 and 4:1 ; O well (iii) the length of the wood particles is between more than 1 mm and less than 5 mm and in which the ratio between the weight of the sand (24a) and the wood particles is between 4:1 and 5:1 . 11. A system (10) of artificial grass comprising: a turf mat (12A) having a plurality of separate synthetic turf blades (20) attached to a backing layer; the underlayment layer (14) is formed, at least partially, from expanded polyethylene or polypropylene bead material having a density in the range of 45-70 g/l; and a padding material (24) according to claim 1 dispersed on the grass mat (12A) between the blades (20) of grass, the padding material (24) further including sand (24a). The artificial turf system (10) of claim 11, wherein the turf mat (12A) and infill material (24) disposed on the turf mat (12A) define a first spring constant and the subfloor layer (14) defines a second spring constant that is more conformal than the first spring constant, in which the second spring constant of the subfloor layer (14) is associated with a deflection control layer and the subfloor layer (14) further defines a third spring constant associated with a center section, such that the first constant of the spring is stiffer than the third spring constant and the third spring constant is stiffer than the second spring constant, or wherein the underlayment layer (14) includes a plurality of projections disposed across an upper bearing surface of the underlayment layer in contact with the turf mat (12A). A process for making an infill material (24) according to claim 1 for an artificial turf system, the process comprising the steps of: sectioning a rough wood disc, the rough disc having a cross-sectional plane to a wood grain structure, the raw discs having a moisture content in a range of about 10% to about 50% by weight; forming wood particles (24b) having a length dimension of the oriented particle generally parallel to the grain structure of the blank, the length dimension in a range of about 1 mm to about 10 mm; controlling the moisture content of the wood particles (24b) after the forming step in a range from about 10% to about 40% by weight; tumbling or abrading the wood particles (24b) so that the edges of the wood particles (24b) are smoothed as compared to a surface cut from the forming step having a sharp, angular edge shape; and controlling a content of wood particles (24b) in a wood bark material to less than about 10 percent by volume of the wood bark material. The method of claim 13, wherein after the step of forming the wood particles (24b), a step of controlling the size of the wood particles (24b) is performed with a notch separator, the size of the wood particles (24b) having a length dimension in a range of about 1 mm to about 10 mm, the length and one of the width or thickness dimensions controlled to an aspect ratio within a range of 4:1 to 10:1, wherein the moisture content of the wood particles (24b) is leads to a range of about 10% to about 25% before the step of controlling the size of the wood particles (24b); O well wherein the step of controlling a wood particle (24b) content further includes controlling a wood particle (24b) content to at least about 70 percent with the particle length dimension generally parallel to a wood structure. the grain of the particle.